This invention relates to a metal interconnection for use in a semiconductor device having a single or multilevel interconnection structure and a method for forming the same. More particularly, it relates to a highly reliable metal interconnection advantageously applicable to finer semiconductor devices.
One commonly used method for forming a metal interconnection or wiring in prior art fine semiconductor devices including multilevel interconnection structures is by providing an underlying metal film (or conductive film) based on a high melting point metal compound such as titanium nitride (TiN), depositing an interconnecting metal film of a conductor containing Al or Al alloy thereon, and processing the deposited metal film into a desired pattern.
The underlying conductive film of a high melting point metal compound is formed at contacts between interconnecting aluminum or aluminum alloy and a silicon diffusion layer as a diffusion barrier layer or barrier metal for preventing interdiffusion of aluminum and silicon. It is effective for preventing the interconnecting metal from undergoing undesirable reaction where it is connected to silicon substrate or the like such as spiking of aluminum or interconnecting material into a shallow diffusion layer and precipitation of substrate silicon in aluminum interconnection as often seen as a result of miniaturization and higher integration. It is also effective for preventing stress-induced migration from occurring when tensile stress is applied to the metal interconnection from an insulating film formed on the metal interconnection.
In forming the high melting point metal compound film such as TiN, reactive sputtering, sputtering of a Ti film followed by nitridation, or chemical vapor deposition (CVD) is used. In depositing the interconnecting metal film such as an Al or Al alloy film, sputtering or CVD is used. It is known that the TiN films formed by reactive sputtering and sputtering of a Ti film followed by nitridation have strong (111) preferential orientation.
M. Kageyama et al., 29th Annual Proceedings, Reliability Physics Symposium, p. 97, 1991 reports that both the TiN film (underlying metal film) and the Al (interconnecting metal film) have (111) planes of the same atom arrangement and a very close atomic distance. Then on the TiN film of (111) preferential orientation is deposited an Al or Al alloy film which is also of (111) preferential orientation. As the Al or Al alloy film is enhanced in (111) orientation, the resulting interconnection is improved in electromigration immunity.
With respect to the deposition of a metal film of a conductive material containing Al or Al alloy as the interconnecting metal film, for example, K. Sugai et al., Proceeding of the 10th International IEEE Multilevel Interconnection connection Conference, p. 463, 1993, discloses that an Al film is deposited on the TiN film by a CVD process using dimethylaluminumhydride (DMAH).
However, it has never been reported that an Al or Al alloy film of enhanced (111) preferential orientation is formed by a CVD process using DMAH or similar reactant.
In miniaturized semiconductor devices, when metal interconnection is formed in fine connection holes, typically contact holes and via holes in an insulating film, the holes are not effectively filled up with the underlying metal film and/or interconnecting metal film, leaving the problems that voids are formed in the holes and the metal interconnection is broken at the hole side wall. With respect to this problem of poor fill-up ability, it was proposed to carry out aluminum deposition by CVD at a lower temperature of 130.degree. C. (see K. Sugai et al., Proceeding of the 10th International IEEE Multilevel Interconnection Conference, p. 463, 1993), but at the sacrifice of deposition rate and productivity.